c++ - 仅初始化结构或数组的前 n 个成员

Question

我正在使用 RAD studio 10.2 附带的 clang 编译器(我认为是 c++ 11)。我今天错误地发现可以使用通常的大括号来分配结构或数组的前 n 个成员，例如

int a[500]={1};
struct {int a,b,c;} st={2,3};

上面的编译和工作正常，但我从来没有遇到过这个或见过它以前使用过，我在网上找不到它的提及(也许我正在使用错误类型的措辞进行搜索)。这个 C++ 有文档吗？

Answer 1

对于 aggregate initialization ,

(强调我的)

If the number of initializer clauses is less than the number of members and bases (since C++17) or initializer list is completely empty, the remaining members and bases (since C++17) are initialized by their default member initializers, if provided in the class definition, and otherwise (since C++14) by empty lists, in accordance with the usual list-initialization rules (which performs value-initialization for non-class types and non-aggregate classes with default constructors, and aggregate initialization for aggregates).

这意味着，对于 int a[500]={1}; ，第一个元素被初始化为 1并且数组的其余 499 个元素被值初始化为 0 .对于 struct {int a,b,c;} st={2,3}; ，成员(member) a初始化为 2和 b初始化为 3 , 最后一位成员 c被初始化为 0也。